open problems in terrestrial planet formation：在类地行星形成的开放问题

Open problems in terrestrial planet formation,Sean RaymondLaboratoire dAstrophysique de Bordeaux,with audience contributions welcome!,How did the Solar System form?,Simulations can roughly reproduce the masses and orbits of Earth and Venus (OBrien et al 2006; Kenyon Raymond et al 2004)Goal: Reproduce inner solar system Constrain Jup, Sats orbits at early timesTest relevant physics,Constraints,Masses, orbits of terrestrial planetsMars small mass is a mystery (Wetherill 1991, Chambers 2001)Very low eccentricities (OBrien et al 2006)Structure of asteroid beltSeparation of S, C typesNo evidence for remnant embryos (gaps)Accretion timescales from Hf/W, Sm/NdEarth/Moon: 50-150 Myr (Jacobsen 2005; Touboul et al 2007)Mars: 1-10 Myr (Nimmo Muralidharan et al 2008),Stronger Constraints,Dust (m),Planete-simals (km),Cores Embryos,Earth-sized planets,104-5 yrs,105-7 yrs,107-8 yrs,Gas giants,Initial conditions for late-stage accretion,Planetary embryos (aka protoplanets) form by runaway and oligarchic growth: Moon-Mars sized (105-6 yrs) (Kokubo & Ida 1998, Leinhardt & Richardson 2005)Late-stage accretion starts when local mass in embryos and planetesimals is comparable (Kenyon & Bromley 2006),Kokubo & Ida 2002,(Giant planets must form in few Myr, so they affect late stages),Key factors for accretion,1. Giant Planets (Levison Desch 2007),Nice model 2 (J, S in 3:2 MMR),No Mars analogsEmbryos in asteroid beltInconsistent with observed structure if embryo Mars-mass or larger,Nice model 2 (J, S in 3:2 MMR),No Mars analogsEmbryos in asteroid beltInconsistent with observed structure if embryo Mars-mass or larger,Nice model 2 (J, S in 3:2 MMR),Eccentric Jup, Sat (e0=0.1),Eccentric Jup, Sat (e00.1),Strong secular resonance (6) at 2.2 AUMars consistently forms in correct configurationEarth and Venus are dry,Inconsistent with Kuiper Belt structure no migration of giant planets possible (Malhotra 1995, Levison & Morbidelli 2003),Influence of giant planets,Raymond, OBrien, Morbidelli, & Kaib 2009,Influence of giant planets,Raymond, OBrien, Morbidelli, & Kaib 2009,Hard to form low-e, highly concentrated terrestrial planet systems,Mars,Small Mars forms naturally if inner disk is truncated at 1-1.5 AU (Agnor et al 1999; Hansen 2009)Can reproduce all 4 terrestrial planets if embryos only existed from 0.7-1 AU (Hansen 2009),Hansen 2009,Other effects,Gas disk effects:Type 1 migration (McNeil et al 2005; Morishima et al 2010)Secular resonance sweeping (Nagasawa et al 2005; Thommes et al 2008)Collisional fragmentation (Alexander Kokubo, Genda),Morishima et al 2010,Jin et al (2008) disk,Assume MRI is effective in inner, outer disk but not in betweenAt boundary between low, high viscosity, get minimum in densityOccurs at 1.5 AUExplanation for Mars small mass?,Jin et al (2008),Summary,No tested configuration of Jup, Sat reproduces all constraints (Raymond et al 2009)Closest is eccentric Jup, Sat but Earth is dry and JS not consistent with Kuiper BeltIncluding gas disk effects doesnt solve the problem (Morishima et al 2010)Hard to reproduce Mars small sizeStrong constraint on Jup, Sats orbits at early timesWas there just a narrow annulus of embryos? (Hansen 2009)Whats missing?Secular resonance sweeping during disk dispersal (Nagasawa et al 2005, Thommes et al 2008)Something else?,Recent progress,Morishima et al 2008, 2010Raymond, OBrien, Morbidelli, Kaib 2009Hansen 2009Thommes, Nagasawa & Lin 2008OBrien, Morbidelli & Levison 2006Raymond, Quinn & Lunine 2006Kenyon & Bromley 2006Nagasawa, Thommes & Lin 2005Kominami & Ida 2002, 2004Chambers 2001Agnor, Canup & Levison 1999,Initial conditions,Start of chaotic growth phase (Wetherill 1985; Kenyon & Bromley 2006)Equal mass in 1000-2000 planetesimals and 100 embryos (5 ME total)Embryos is Mars vicinity are 0.1-0.4 Mars massesIntegrate for 200 Myr + with Mercury (Chambers 1999),Cases,Current Jup, SatJup, Sat wi